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United States' Michael Phelps displays his gold medal for the men's 100-meter butterfly swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London, Friday, Aug. 3, 2012. (AP Photo/Matt Slocum)

Gabrielle Douglas of the U.S. competes on the balance beam during the women's individual all-around gymnastics final in the North Greenwich Arena during the London 2012 Olympic Games August 2, 2012.

Tyler Clary of the U.S. sings his national anthem with his gold medal on the podium after winning the men's 200m backstroke final during the London 2012 Olympic Games at the Aquatics Centre August 2, 2012.

United States' Rebecca Soni celebrates winning gold and setting a new world record in the women's 200-meter breaststroke swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London, Aug. 2, 2012.

Team USA reacts after winning the gold medals at the victory ceremony after the women's eight finals rowing event during the London 2012 Olympic Games at Eton Dorney August 2, 2012.

Ranomi Kromowidjojo of the Netherlands holds her gold medal during the women's 100m freestyle victory ceremony at the London 2012 Olympic Games at the Aquatics Centre August 2, 2012.

Kohei Uchimura of Japan celebrates winning a gold medal during the men's individual all-around gymnastics final in the North Greenwich Arena during the London 2012 Olympic Games August 1, 2012.

China's Zhang Jike celebrates after defeating China's Wang Hao in their men's singles gold medal table tennis match at the ExCel venue during the London 2012 Olympic Games August 2, 2012.

Members of Italy's fencing team celebrate after winning against Russia in their women's foil team gold medal match at the ExCel venue during the London 2012 Olympic Games, August 2, 2012.

Gabrielle Douglas of the U.S. competes in the balance beam during the women's individual all-around gymnastics final in the North Greenwich Arena during the London 2012 Olympic Games August 2, 2012.

South Korea's Ki Bo-bae celebrates on the podium after her gold win over Mexico's Aida Roman during the individual archery competition at the 2012 Summer Olympics, Aug. 2, 2012, in London.

China's Ye Shiwen poses with her gold medal on the podium during the women's 400m individual medley victory ceremony at the London 2012 Olympic Games at the Aquatics Centre July 28, 2012. Ye smashed the world record to win the gold medal on Saturday with

Gold medallist Teddy Riner, of France, holds his bouquet at the victory ceremony for the men's +100kg judo event.

Great Britain's Heather Stanning and Helen Glover celebrate after winning the gold medal for the women's rowing pair in Eton Dorney.

Serena Williams of the U.S. returns to Russia's Maria Sharapova in their women's singles gold medal match at the All England Lawn Tennis Club during the London 2012 Olympic Games August 4, 2012.

Britain's Mo Farah holds the Union Flag after winning the men's 10,000m final at the London 2012 Olympic Games at the Olympic Stadium August 4, 2012.

Gold medalist Britain's Jessica Ennis poses on the podium of the heptathlon at the athletics event during the London 2012 Olympic Games on August 4, 2012 in London.

China's Li Xuerui (R) and compatriot Wang Yihan pose with their gold and silver medals respectively after their gold medal women's singles badminton match at the London 2012 Olympic Games in London, August 4, 2012.

Jamaica's Shelly-Ann Fraser-Pryce celebrates after winning the women's 100m final at the athletics event of the London 2012 Olympic Games on August 4, 2012 in London.